PROPOSAL: Add another method for deletion

[goldeneggg]

Hi everyone. This is my proposal pull-request.

I'd like an another generated method named by DeleteByModel. This method removes a single record of assigned obj argument and validly executes some defined gorm's callbacks

Usage

1. Define your model design

// example
    Model("Dummy", func() {
      RendersTo(DummyMedia)
      Description("Dummy Model Description")
      Field("id", gorma.Integer, func() {
        PrimaryKey()
        Description("This is the Dummy Model PK field")
      })

      Field("dummy_name", gorma.String, func() {})
      Field("created_at", gorma.Timestamp, func() {})
      Field("updated_at", gorma.Timestamp, func() {})
    })

2. If you will geenerate models by goagen gen -d=YOUR_PATH --pkg-path=github.com/goadesign/gorma, target model files have DeleteByModel method.

// Delete removes a single record.
func (m *DummyDB) Delete(ctx context.Context, id int) error {
  :
}

// *New generated method*
// DeleteByModel removes a single record of assigned model.
// If record is deleted by this method, some defined callbacks of gorm are executed too.
func (m *DummyDB) DeleteByModel(ctx context.Context, obj *Dummy) error {
  defer goa.MeasureSince([]string{"goa", "db", "dummy", "deleteByModel"}, time.Now())

  err := m.Db.Delete(obj).Error
  if err != nil {
    goa.LogError(ctx, "error deleting Dummy", "error", err.Error())
    return err
  }

  return nil
}

Example

If record is deleted by DeleteByModel method, some defined gorm's callbacks(including BeforeDelete, AfterDelete) are validly exected too.

An example as follows:

// Define "AfterDelete" gorm's callback
func (d *Dummy) AfterDelete() (err error) {
  fmt.Printf("ID = %d", m.ID)
  return
}

// Delete using "Delete(ctx, id)" method
m.Delete(ctx, 1)  // will display "ID = 0", because receiver of AfterDelete is an empty object

// Delete using new "DeleteByModel(ctx, obj) method
d = m.Get(ctx, 1)
m.DeleteByModel(ctx, d)  // will display "ID = 1"

[raphael]

The proposal looks good to me. Could we call the method DeleteModel instead? seems to flow a bit better. Also for the header comment maybe something like the following is a little bit clearer?

// DeleteModel removes a single record given the corresponding model.
// Exisiting gorm deletion callbacks are executed if a record is deleted.

Finally do you think you could add a few tests? thank you!

[goldeneggg]

Thank you for your quick reply!

do you think you could add a few tests?

OK. It's working properly only in our private project. )) Should I just add tests of DeleteByModel?